1. Field of the Invention
The present invention relates to a game machine in which a game proceeds according to a game program or according to operations of a player and, more particularly, to a game machine in which display means represents a three-dimensionally processed image.
2. Description of the Related Art
In recent years, the game industry has employed a method in which three-dimensional computer graphical images are positioned in the world coordinates and are then rendered on a projection screen as two-dimensional images.
The three-dimensional image is usually formed by a computer graphic designer through use of, for example, a plurality of polygons. A texture is pasted to the respective polygon, thereby representing a pattern or a color.
As mentioned above, in the state in which a plurality of three-dimensional images are positioned in the world coordinates and are rendered on a projection screen in consideration of information about the depth of each apex of the respective polygon, all the three-dimensional images are two-dimensionally rendered on the projection surface while in focus.
Incidentally, when capturing a scenic view, the human eye recognizes in-focus areas clearly but out-of-focus areas blurry. This applies to a photographic image; an in-focus area is clearly represented but an out-of-focus area appears blurry.
To the best of the knowledge of the present applicant, there exists no game machine which performs three-dimensional computational processing according to a game program and operations of the game player, as necessitated, and in which display means renders an image on a game screen in consideration of focus.
In other words, there are game machines which present a blurred image, such as that mentioned previously, on a demonstration screen other than a game screen—in which an image appears on display means—that is, a screen which demonstrates introduction of a game before starting of the game or a screen which does not involve player's commitment at all. However, there exists no game machine which considers the aforementioned blurring for unpredictable animated characters in accordance with the progress of the game.
A further explanation is now given of “focus.” The general term “game” encompasses driving games, battle games, and shooting games. In the case of these games, the polygon that is positioned nearest to the player in the world space relative to the projection screen is not necessarily in focus. If the polygon positioned nearest to the player is in focus and rendered on the projection surface, and if the polygons positioned behind the nearest polygon are blurred in proportion to their respective depths, the player may have difficulty in playing the game.
For instance, in the foregoing shooting game, the player aims a gun at an image rendered on the projection surface, i.e., a target displayed on a CRT monitor of the game machine. At this time, the target is not necessarily positioned nearer to the player than is the projection surface. Objects such as drum cans which cannot be targets may be positioned in front of the target. Further, even when a plurality of targets are displayed on the monitor, the player does not necessarily aim at and shoot the target nearest to him.
Therefore, blurring of a target in proportion to its depth cannot be easily and simply applied to the field of game machines.
For reference, the technology of providing blurred representations employed in fields other than the game machine field will now be described.
For example, Japanese Patent Application Laid-open No. 8-63614 describes techniques for determination of a distance between an in-focus surface and a polygon, blurring of mapped data, and coordination of the mapped data. The term “coordination” is related to a texture mapping method and signifies pasting of a two-dimensional graphical pattern (i.e., mapped color data) to a three-dimensional image (i.e., an object), thereby representing the nature of the object. This definition is found on pg. 2, column 2, in lines 18 to 22 of Japanese Patent Application Laid-open No. 8-63614. However, the previously-described prior art (Japanese Patent Application Laid-open No. 8-63614) fails to describe a specific method of blurring objects in consideration of the distance between an in-focus surface and polygons serving as objects of display (i.e., objects).
In the field of computer graphics, a distributed ray-tracing method has already been known as a technique for providing blurred representations. This method involves calculating, through simulation, how objects located at positions other than an in-focus position are blurred by means of a lens effect, as required. Therefore, the method has a problem in that blurring of one screen display requires several tens of minutes. Therefore, the method can be applied only to a static image. However, in a field, such as the computer game field, that requires animating operations, there have already been established standards that define the time required for scanning one screen as {fraction (1/60)} or {fraction (1/50)} seconds. In view of processing speed, a CPU commonly used for a game is substantially unable to simultaneously satisfy the standards and to represent naturally-animated characters on the display means of the game machine, such as a monitor.
In the case of production of a three-dimensional animation through use of images blurred by the foregoing computer graphics technology, before broadcasting the animation a sufficient time is spent in preparing a great number of image data sets through perspective transformation, and animated character can be represented by interchanging of the image data sets. However, in the case of a game, images to be displayed cannot be determined univocally, and images change in accordance with various possibilities according to the progress of the game. Therefore, the images must be represented through computation processing, as required.